Hub assemblies have been used in the construction of exhibit display stands and dome-like structures such as geodesic domes. For maximum utility, designs which minimize the number of small parts, minimize part count, minimize the number of free components when disassembled, and maximize the stiffness are particularly valuable.
U.S. Pat. No. 3,968,808 discloses a collapsible self-supporting dome-like structure with a network of pivotal rods interconnected with linking joints. The linking joint holds six rods, each connected to a six-sided metal ring. Each rod is connected onto the ring and is capable of rotating. The rod is a permanent attachment and thus cannot be disconnected nor replaced. There does not appear any way to attach a cover to the dome-like structure such as is found in the “keeper” component in the articulating hub assembly of the present invention.
U.S. Pat. No. 4,026,313 also discloses a collapsible self-supporting dome-like structure with a network of pivotal rods interconnected with linking joints. The pivotal device linking the rods together forming the structure is a circular joint. Each joint has only four rods. Each rod contains a plug ending with a small cylinder. This small cylinder is nested inside the joint and allows the rod to rotate. It appears that none of the components is easily interchanged. The top and bottom sections of the hubs in the reference appear to be permanently joined by an adhesive so that none of the rods or plugs can be replaced.
U.S. Pat. No. 4,512,097 discloses a display panel mounting clip. The clip body is used to connect display panels together. The clip assembly disclosed requires a spring mechanism to create tension and hold the panels together. The present invention requires no springs. The clip disclosed in the reference must be snapped into an opening joining the rods in a circular joint. In the present invention, the keeper is screwed into the hub body so it is threadedly secured.
U.S. Pat. No. 4,280,521 discloses a hub assembly for collapsible structures. The hub assembly disclosed in the reference requires a circular retaining ring to hold the “column like elements” or tubes in place. Each tube must be threaded onto a circular retaining ring prior to insertion into the hub section. The hub sections are secured in place by use of an adhesive to fuse the two hub sections together permanently. The tube members within the structure, therefore, are not easily replaceable since the hub sections cannot be replaced without destroying them. The reference design uses a three piece clamping device to hold or attach a skin or cover to the structure. One piece is a plug that is incorporated inside the hub section and is fused into the hub sections. The second piece is a flat disc. The third piece is an element which is a screw. The screw is threaded into the plug and holds the clamp down. A screw driver would obviously be required to remove the clamp if the cover, the skin or the tubes have to be replaced.
In the present invention no circular ring is present or required to hold the rods together inside the hub, reducing the number of components. In addition, a screwdriver is not required to disassemble the present invention. Further, the design taught by '521utilizes a single tang design. Single tang designs are inherently flexible, an issue addressed by the present invention. Further, the reference design does not provide a means to restrict rotation of the tubes that connect to the hub assembly without the use of an adhesive or other welding method. In the present invention an adhesive is not required.
U.S. Pat. No. 5,797,695 also discloses a hub assembly for collapsible structures. The hub assembly disclosed in the reference employs a design comprised of a single tang connected to a separate plug. This design secures the tube to the body of the hub assembly with an assembly consisting of a plug, tang, roll pin and rivet, presenting the user with four small, easily misplaced, and damaged parts at each tube position. The reference assembly provides for eight positions, thus users must account for 32 such parts in total when repairing to assembling the assembly or structure.
The single tang design also permits the plug and attached tube to bend in the direction perpendicular to the plane of the tang, an undesirable feature when the hub assembly is used in collapsible structures. Lateral weakness results because a single tang design requires the tang to resist bending forces in its weakest direction, making the tang susceptible to forming a permanent bend or fracture, an undesirable failure mode addressed by the present invention. Also, in the '695 design, the position of the tang along the roll pin is not fixed, resulting in bending when mispositioning of the tang on the roll pin occurs, an issue addressed in the present invention. Finally, the hub assembly disclosed in the reference employs a rivet in the side wall at the end of each tube to secure the tang's tail to the plug and tube. The rivet is a small, easily misplaced part that requires special tools for removal and replacement in the event repair is required and holes in the side wall of the ends of the tubes must be provided to accept the rivet. The hole in the side wall of the tube weakens the tube, making the tube more susceptible to failure than tubes used with the present invention. Provision of said holes requires the availability of additional special tooling to effect a field repair or the availability of application-specific tubing with holes provided.